It is widely recognized that changes in the sleep/wake system accompany the aging process. As a consequence, a large proportion of older people complain of significant sleep disturbance-Age-related sleep changes are commonly expressed as shallow and fragmented sleep, and multiple, often prolonged awakenings, particularly in the second half of the night. Few older subjects report difficulties getting to sleep. Therefore, sleep disturbance in people over 65 is generally considered to be a disorder of maintaining, rather than initiating, sleep. Recent evidence indicates that timed exposure to bright light can be effective in managing these age-related sleep changes by acting directly on the circadian timing system. Yet, effectiveness, of light treatment may be compromised by compliance problems associated with the time required for, and the constraints involved in, the treatment regimen. Response to treatment is likely to be affected also by one's recent history of light exposure. Until issues of compliance are fully understood and effectively dealt with, light treatment for age-related sleep disturbance cannot be employed to its full potential. This COMPETING CONTINUATION will examine three important issues related to compliance: First, it is proposed to quantify the effects of prior light history on the phase-shifting capacity of bright light. Second, a novel procedure for light delivery will be tested, the development of which may hold promise for significantly enhancing user compliance. Finally, an in-home treatment will be implemented which administers light in a manner that may be more acceptable to patients. In the lab-based studies, circadian variables of young (<30 yrs) and older subjects (>65 yrs) will be monitored at baseline, and throughout an interval during which subjects' prior light history is controlled, immediately preceding exposure to 1) a conventionally-administered bright light phase-shifting stimulus, or 2) a bright light phase-shifting stimulus administered using a non-ocular site for phototransduction. In the treatment study, two groups of healthy, older subjects (>65 yrs) who complain of sleep maintenance insomnia, and whose complaints are verified polygraphically, will undergo either 1) a one-month regimen of timed room-light exposure combined with timed light avoidance, or 2) a well-validated control condition, while living at home and continuing normal daily activities. All three studies address issues crucial to the successful development and implementation of bright light treatment.